


Brittle Walls

by TeeGee



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Developing Relationship, F/M, First Time, Masturbation, Ohhh boy, Oral Sex, Semi Public Sex, Sexual Tension, Some tenderness, of the resolved kind, seteth is a bit sexually repressed and byleth just gets to him A Lot, the subtlest of dom/sub undertones, this is mostly just horny I apologize
Language: English
Status: Completed
Published: 2020-10-22
Updated: 2020-10-22
Packaged: 2021-03-09 00:46:46
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,125
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27155422
Author URL: https://archiveofourown.org/users/TeeGee/pseuds/TeeGee
Summary: In one swift motion Byleth had knocked the feet out from under Seteth’s body with a strong sweep of her lance and he hit the ground with a low grunt. He quickly tried to scramble into a sitting position to get up. The pressure of a heel against his chest and the tip of a wooden Lance against his throat stopped him dead in his tracks.At what point in their spar had he gotten this hard?
Relationships: My Unit | Byleth/Seteth
Comments: 4
Kudos: 61





	Brittle Walls

**Author's Note:**

> Hey folks! I, uh, wrote most of this drunk last weekend and just finished it up today at 1am. That's all I have as far as excuses go here.

The sound of wooden weapons clanking against each other intersected with the grunts of exertion echoed through the mostly empty halls of the training grounds.

Seteth and Byleth were sparring late at night, illuminated by only the last few torches that were still burning by the square of dirt they were moving about on. They encountered each other in this place about half an hour ago. The professor had walked in on Seteth getting in some lance practice in peace after everyone else had left for the night. After she had carefully watched his movements for a while Seteth had turned around, asking her if he could help her somehow. “Spar with me.” She had simply stated, picking up a training lance on her own and striding towards the middle of the training ground. 

So now here seteth was, trying not to lose his cool as byleth, her coat long laid aside to grant her more movement, was actually giving him a hard time.

He had learned over her time at the academy that the former mercenary was certainly a skilled fighter with much practical knowledge about all kinds of weapons, but he hadn't expected her to measure up to his own skills which he had honed over the centuries.

It certainly also didn't help that seteth found himself distracted by the unusual sight of byleth without her coat, her strong form and wide hips even more pronounced than in her everyday attire.

"You fight well.” Byleth huffed after he parried one of her blows. “I hadn't expected you to be able to lead a weapon as well as you lead a quill." She grunted out, dodging his retaliation and meeting his gaze, holding steady eye contact as they both took a break from attacking, circling each other and catching their breath. Though seteth found himself shocked at his thought that it also felt like another kind of observation, a much more charged dance around each other than simple colleagues in a spar. 

"Well, there are many things you don't know about me." He replied with a smirk, challenge in his tone while his mind screamed at him that _he really didn't want Byleth to find out all those things… yet._

He kicked his own mind back into silence at that last word and charged Byleth as a distraction from his own thoughts more than anything else.

She parried the blow of his wooden Lance with her own once more and quickly they were fully engaged in mock combat again. 

"You fight pretty good as well." He stated after a few blows. "I haven't seen much of you in a fight yet myself, though the reports always talked highly of you." 

"Oh, so you had to leave a lot to your imagination, then?" Byleth replied. Was that a hint of flirting in her tone? Her expression betrayed nothing of the sort and seteth quickly tried to clear his mind of any implications he kept seeing in her behavior before he made a fool of himself.

But it was too late. 

In one swift motion Byleth had knocked the feet out from under Seteth’s body with a strong sweep of her lance and he hit the ground with a low grunt. He quickly tried to scramble into a sitting position to get up. The pressure of a heel against his chest and the tip of a wooden Lance against his throat stopped him dead in his tracks.

At what point in their spar had he gotten this hard? 

"Give it up, big guy. You're mine." Byleth said playfully while looking down at him.

His cock twitched in his pants at her words and seteth was grateful for the thick fabric of his tunic helping in hiding his predicament. 

"I yield. You win." He breathed out in defeat, slumping back and cursing himself internally for finding his sparring partner as distracting as he did.

The Lance, as well as the pressure against his chest, disappeared and Seteth took in a deep and shaky breath, trying to sort himself out.

"Well fought." He grunted while getting up and patting down his coat, careful to avoid the front where he could still feel the uncomfortable strain of his erection against the seam of his smallclothes. This was embarrassing. Seteth knew he should add something more, make some smalltalk to hide his wounded pride at being bested but he found himself out of words and mostly just wanted to get out of this situation to think about what was happening between them. 

Or try and forget all about it. He hadn’t decided yet.  
  
“You held up pretty well yourself.” Byleth said. “To be quite honest with you I didn’t believe Catherine at first when she pointed to you as one of the strongest fighters in the monastery, but I see what she means now.”  
  
Seteth chanced a glance towards the Professor to find her looking at him intensely in the dim, flickering light of the torches. Her eyes were unreadable as they moved up his form until they met his gaze.  
  
Seteth gulped and took a step back after a few seconds before turning to put his training lance away into the rack by the wall. “We should turn in for the night soon, Professor.” He said, facing the rack while talking to her. “Tomorrow will be a busy day. With the preparations for the ball starting in earnest and all that.”  
  
Byleth appeared at his side, placing her own weapon back where it belonged and murmuring as if to herself: “Yeah, that sounds like the reasonable thing to do.” She turned to him with a soft smile, gently touching his arm as she spoke up. “Good night then, Seteth. And take care.”  
  
With that she turned around and left in a flurry, the step of her heels softly echoing through the room until she quietly slipped through the door leading to the training area with one last wave towards him, which he answered in kind while wishing her a good night as well, and carefully let it slam back shut behind her.  
  
Seteth’s back hit the cool stone wall next to the weapon rack as he leaned against it. What a fool he was. Losing a fight because he found himself distracted by his opponent’s body. He pressed his eyes shut, trying and failing to get the images of her swaying hips and muscular shoulders out of his mind. He had known that he found himself attracted to Byleth before now, but their close encounter tonight made him realize just how far gone he was.  
  
And he didn’t quite know what to make of it. Had she been flirting with him tonight? Or had he been reading too much into her subtle expressions and smug words?  
  
His mind provided him with the memory of her standing above him, pinning him to the ground with her heel on his chest.  
  
_Give it up, big guy. You're mine_

A choked noise escaped Seteth’s throat as his hand pressed against the bulge in his pants, finally giving his cock some attention. He should probably scramble back to his room and take care of himself there, but his knees felt like jelly and he felt as if he’d fold in on himself without the support of the stone wall.  
  
With a low curse under his breath he quickly unclasped the belt holding his robe together around his waist, giving him better access to his pants which he quickly unbuttoned to free his aching cock. He’d be quick about it, more practicality than anything. The last thing he needed was one of the night guards checking in here and catching the church’s second in command with his pants around his ankles.  
  
He began to pleasure himself with quick, deft strokes. He left all shame aside for the moment in favour of getting this over quickly, indulging in whatever scenarios his brain provided him with. He imagined Byleth and the noises she’d make as he fucked her relentlessly at the same pace at which his hand currently moved over his own length. Her usually so passive face warped in pleasure and her full breasts bouncing with every quick thrust into her. It was base and filthy and he’d need to have a serious debate with his consciousness later, but for now Seteth just completely let go and lost himself in the pleasure.  
  
With this much focus on himself he didn’t hear the creak of the large wooden door as it opened just enough for someone to slip through.  
  
“Sorry, I just realised I forgot my coat he- _Oh my._ ” Byleth’s voice brought Seteth tumbling back to reality in the worst way possible. He quickly scrambled to cover his crotch by pulling his robe closed over it in a vain attempt to hide what he had been caught doing.  
  
“Professor!” he exclaimed in horror. “I am _so_ sorry I-” He stopped when she held up a hand. “It’s okay, Seteth.” She said, not quite able to keep a slight chuckle out of her voice. “As I was saying: I just need to get my coat and I’ll be gone.” Seteth watched her walk into the room, paralyzed where he was and still bunching the fabric in his hands to cover his crotch. She wasn’t running away in disgust at him as she ought to. _He_ wasn’t running away in disgust at himself as he ought to. There was only the sound of his laboured and shameful breathing as she picked up her coat and turned to walk back towards the entrance again. It was only a few short seconds but for Seteth they felt like they lasted forever. Time seemed to stop completely as Byleth came to a halt on her way back and turned towards him, lower lip between her teeth and eyeing his body, before asking: “Do you want help with that?”  
  
A shudder ran down his spine. “N-no... It’s alright.” He stammered out.  
  
She looked up into his eyes then. “What if I _want_ to help you out?”  
  
Seteth took in a sharp breath but didn’t say anything.  
  
Byleth took a careful step towards him as if approaching a wounded animal. “After all…” another step. “I’m the reason I found you like this,” another step. “aren’t I?”  
  
“Yes.” Seteth breathed, as if only admitting it to himself. “I’m afraid you are.”  
  
“Then let me help you.” She was right in front of him now. “It’s only fair, don’t you think?”  
  
Seteth gulped. This must still be his fantasy. His mind had just run away from him and decided to torture him.  
  
He nodded.  
  
“Let me hear you say it.” She prompted.  
  
“Yes… yes I want you. I need you.” He answered her. Screwing his eyes closed as he admitted his sin.  
  
Byleth dropped her coat back down onto the ground before him before kneeling down on it. She gently placed her warm hands over his own where they were still doing their best to hide his cock from view. Her soft touch made Seteth uncramp his fingers and let his hands be guided to the side.  
  
He let go of the cloth and fumbled with his hands at his sides for a second before firmly placing them on the wall behind him.  
  
“Relax.” Murmured Byleth, looking up from where she had taken in the newly revealed sights to glance up and him with her deep blue eyes. “Unless you’re having second thoughts?”  
  
Seteth wished he did. Instead he replied “No… I want this. It just… it has been a while since I’ve found myself in a position such as this.” He cleared his throat.  
  
“I understand…” Byleth said gently, though Seteth highly doubted that she truly understood the implications that the term _‘a while’_ had for him. “I won’t hurt you. You don’t have to be afraid.” To punctuate her point she placed a series of gentle kisses on his exposed hip and Seteth took a deep breath, relaxing his muscles as he exhaled, even as his body was still on fire with lust and anticipation. “There we go.” Byleth said reassuringly with a gentle smile that he found himself returning despite it all. It had truly been a long while since he had shared such an intimate moment with anyone. He rarely found himself involved in such trysts and whenever he had given in in recent centuries he would soon be gone and not be spotted in that corner of the continent for the next few decades.  
  
With Byleth he didn’t have that option. Unless he wanted to have to explain some specifics to Rhea, he couldn’t just run away from his weaknesses in this instance. But strangely enough he found himself trusting Byleth. He wanted her and she wanted him and it thrilled him to no end, even if he didn’t know where their relationship would go from here yet and so he decided to let her take whatever she wanted from him in this encounter. Whatever it was he trusted her to not take too much.

Confident in his comfort, Byleth finally placed her hand loosely around Seteth’s cock and started to move it up and down his shaft, still looking up at him and gauging his reaction. Seteth lifted one of his hands off the wall and placed it in Byleth’s hair, gently threading his fingers through the unruly strands.  
  
“Byleth…” He whimpered after a few more strokes. “Please. I need more of you”  
  
“As you wish.” She replied, licking her lips before diving in and pressing a kiss to his cock’s head. The groan Seteth let out as he watched Byleth part her lips and slowly envelop his shaft in her warm mouth echoed off the stone walls of the open space. It reminded him all too much of where they still were and he quickly clamped his free hand over his mouth while the other’s grip tightened in the professor’s hair.  
  
Byleth’s hand firmly grasped the base of his cock as she slowly started bobbing her head and using her tongue to tease him in the best ways possible. She soon picked up her pace once she got a feel for his size and began letting out little muffled groans similar to the ones spilling out between Seteth’s fingers.  
  
He was absolutely mesmerized by the sight before him. Byleth, on her knees in front of him and eyes closed and eyebrows drawn together in both pleasure and concentration as she sucked his cock was a sight that would burn itself into his memory for a long while. His mind wandered back to his earlier fantasies of him fucking the professor and the prospect that she might want something like that from him had him gasp and he had to hold himself back to not cum right then and there. He wouldn’t last long either way under these circumstances but a selfish part of him wanted to enjoy this for just a bit longer.  
  
As Byleth continued to thoroughly work his cock her breathing became laboured and started to come out in little huffs through her nose. Her movements turned sloppier and a trail of saliva mixed with pre-cum ran down from the corner of Byleth’s mouth. Seteth’s hand in her hair gently began to guide her head to keep a steady rhythm and she relaxed as she let him take over her movements. She opened her eyes to look up at him again and the sight of her this utterly wrecked as he used her mouth for his pleasure was sending him straight to the edge.  
  
_“Byleth.”_ Seteth breathed. “I’m going to-” He didn’t get to finish his sentence as she quickly grabbed his hips and took over again, giving his cock a few more flicks with her devilish tongue and a few hard sucks. He bent over with a quieted scream of her name as he came into her mouth and felt her swallowing around him. It was a few seconds of absolute bliss until Seteth came back to himself, breathing heavily and looking down at Byleth who slowly let his length slip out of her mouth and sat back on her haunches, gasping for air with a satisfied look on her face.  
  
“ There we go.” She said, wiping her mouth with the back of her hand. “You know I thought you weren’t interested and were trying to turn me down when you said we should just turn in for the night. I’m glad to find out that I was wrong.”  
  
“I… I thought I read too much into your actions.” He admitted as he carefully began getting his clothes in order again. “I didn’t want to act on something I wasn’t one-hundret percent sure on.”  
  
Byleth let out a quiet laugh as she got off her knees. “So you wait about ten seconds after I’ve left the room to start jerking yourself off?”  
  
Seteth blushed at her words. “I never said that you didn’t get to me.” He admitted. “Because you did… very much so.”  
  
An awkwardness settled between them as neither of them quite knew how to proceed.  
  
“I suppose you’ll want to talk about this.” She proposed after a few seconds.  
  
“Yes.” Seteth confirmed. “I think we have a few things to discuss.” He hesitantly reached out and brushed a few strands of hair out of Byleth’s beautiful and still flushed face. “Do… do you need help as well?” He murmured.  
  
“I’ll be fine for now… Though if you want to repay me, maybe we can organize that after we talk things through.” She leaned into his hand which had come to rest against her cheek and covered it with her own.  
  
This display of tenderness made Seteth’s heart race. He felt that their encounter wasn’t just about lust and it caused even more conflicted thoughts to flutter through his mind. They really needed to talk.  
  
“Would you happen to have time tomorrow after dinner?” He asked as she picked up her coat and shook some of the dust from the ground off it before flinging it over her shoulder. “I think I have some important… paperwork that I need to go over with you.”  
  
They started to make their way to the training ground’s door together.  
  
“I think I should be free.” She said with a smirk. “If not I’ll gladly put everything aside for your visit. It’s important academy business after all.”

  
Seteth escorted the professor through the quiet of the nightly monastery right up to her door. And as he bid her good night and turned to leave he instead found himself pulled into an achingly tender kiss.  
  
It tasted of secrets and promises and he smiled against her lips. 

**Author's Note:**

> Title from the lyrics of Holy, Holy, Holy by Squalloscope (v/ good setleth song)


End file.
